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Fix alert-exceeds-max feature for files > 2GB and < max-filesize #1032

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micahsnyder
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The --alert-exceeds-max feature should alert for all files larger than 2GB because 2GB is the internal limit for individual files. This isn't working correctly because the goto done; exit condition after recording the exceeds-max heuristic skips over the logic that reports the alert.

This fix moves the ">2GB" check up to the location where the max-filesize engine option is set by clamd or clamscan. If max-filesize > 2GB - 1 is requested, then max-filesize is set to 2GB - 1.

Additionally, a warning is printed if max-filesize > 2GB is requested (with an exception for when it's maxed out by setting --max-filesize=0).

Resolves: #1030

The --alert-exceeds-max feature should alert for all files larger than
2GB because 2GB is the internal limit for individual files.
This isn't working correctly because the `goto done;` exit condition
after recording the exceeds-max heuristic skips over the logic that
reports the alert.

This fix moves the ">2GB" check up to the location where the
max-filesize engine option is set by clamd or clamscan.
If max-filesize > 2GB - 1 is requested, then max-filesize is set to
2GB - 1.

Additionally, a warning is printed if max-filesize > 2GB is requested
(with an exception for when it's maxed out by setting --max-filesize=0).

Resolves: Cisco-Talos#1030
@micahsnyder
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Note: I'm actually a little bit on the fence about the warning when setting max-filesize > 2GB. I expect it will draw a lot of attention. However, a lot of people mistakenly think the limit is 4GB or even unlimited because there is presently no warning.

@ragusaa ragusaa self-requested a review September 27, 2023 19:25
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ragusaa commented Sep 27, 2023

Note: I'm actually a little bit on the fence about the warning when setting max-filesize > 2GB. I expect it will draw a lot of attention. However, a lot of people mistakenly think the limit is 4GB or even unlimited because there is presently no warning.

I like having a warning that a file is not being scanned due to a size limit, so that the user is aware.

@micahsnyder micahsnyder added the 🍒cherry-pick-candidate A PR that should be backported once approved. label Sep 29, 2023
@micahsnyder micahsnyder merged commit 8430de5 into Cisco-Talos:main Oct 19, 2023
22 of 24 checks passed
@micahsnyder micahsnyder deleted the CLAM-2449-max-filesize-gt-2G branch October 19, 2023 20:26
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Heuristics.Limits.Exceeded.MaxFileSize not emitted for 2GB+ files
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